Conventional Fixtures Altman Ellipsoidals
- Thread starterkef
- Start date
Lenses
I had the same problem. I took my light meter and took a reading with the lens part out the light reading was the same, put the lens in took a reading one was darker than the other. Switched the lenses in the housing and the reading switched with the lenses. The lenses got cleaned, no change. My experience.
I had the same problem. I took my light meter and took a reading with the lens part out the light reading was the same, put the lens in took a reading one was darker than the other. Switched the lenses in the housing and the reading switched with the lenses. The lenses got cleaned, no change. My experience.
Les
Well-Known Member
Re: Lenses
Altman updated the glass in their lenses at some (or several) points down the line. Original 360Q's used "coke bottle green" lenses, while later models use white crown glass (I think that's what they call it). Gmff, you may have had a mixed batch, and you might too, kef. Remove the lenses from a "bright" ellipsoidal, and a "dim" ellipsoidal and view them from the side. Do any of the lenses look green or blue? If so, that's your problem. The older lenses experienced lower light transmission. Do this if the problem stays with the unit rather than 'moving' with the lamp cap.
Altman updated the glass in their lenses at some (or several) points down the line. Original 360Q's used "coke bottle green" lenses, while later models use white crown glass (I think that's what they call it). Gmff, you may have had a mixed batch, and you might too, kef. Remove the lenses from a "bright" ellipsoidal, and a "dim" ellipsoidal and view them from the side. Do any of the lenses look green or blue? If so, that's your problem. The older lenses experienced lower light transmission. Do this if the problem stays with the unit rather than 'moving' with the lamp cap.
Re: Lenses
Les is onto something here, as indeed earlier versions of the 360Q used a soda lime glass (thus the greenish tint when viewing the lens) while the later version employed the use of a clearer crown glass. The thickness of this lens type will certainly affect the output of the fixture, and the amount of dirt, dust, grime, etc will exacerbate the problem. (Can I say that on this forum? Exacerbate just doesn't seem, well... proper.)
Wikipedia states in part:
http://en.wikipedia.org/wiki/Crown_glass_(optics)
Crown glass (optics) is produced from alkali-lime (RCH) silicates containing approximately 10% potassium oxide. It has low refractive index (≈1.52) and low dispersion (with Abbe numbers around 60); crown glass is one of the earliest low dispersion glasses...
Soda-lime glass - Wikipedia, the free encyclopedia
Soda-lime glass is prepared by melting the raw materials, such as sodium carbonate (soda), lime, dolomite, silicon dioxide (silica), aluminium oxide (alumina), and small quantities of fining agents (e.g., sodium sulfate, sodium chloride) in a glass furnace at temperatures locally up to 1675 °C...
Soda-lime glass is divided technically into glass used for windows, called float glass or flat glass, and glass for containers, called container glass. Both types differ in the application, production method (float process for windows, blowing and pressing for containers), and chemical composition. Float glass has a higher magnesium oxide and sodium oxide content as compared to container glass, and a lower silica, calcium oxide, and aluminium oxide content.
Les is onto something here, as indeed earlier versions of the 360Q used a soda lime glass (thus the greenish tint when viewing the lens) while the later version employed the use of a clearer crown glass. The thickness of this lens type will certainly affect the output of the fixture, and the amount of dirt, dust, grime, etc will exacerbate the problem. (Can I say that on this forum? Exacerbate just doesn't seem, well... proper.)
Wikipedia states in part:
http://en.wikipedia.org/wiki/Crown_glass_(optics)
Crown glass (optics) is produced from alkali-lime (RCH) silicates containing approximately 10% potassium oxide. It has low refractive index (≈1.52) and low dispersion (with Abbe numbers around 60); crown glass is one of the earliest low dispersion glasses...
Soda-lime glass - Wikipedia, the free encyclopedia
Soda-lime glass is prepared by melting the raw materials, such as sodium carbonate (soda), lime, dolomite, silicon dioxide (silica), aluminium oxide (alumina), and small quantities of fining agents (e.g., sodium sulfate, sodium chloride) in a glass furnace at temperatures locally up to 1675 °C...
Soda-lime glass is divided technically into glass used for windows, called float glass or flat glass, and glass for containers, called container glass. Both types differ in the application, production method (float process for windows, blowing and pressing for containers), and chemical composition. Float glass has a higher magnesium oxide and sodium oxide content as compared to container glass, and a lower silica, calcium oxide, and aluminium oxide content.
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